The present invention relates to a protection circuit for amplifier circuits for protecting the circuit components of an amplifier circuit from deterioration or destruction when power source voltage for the amplifier circuit or the operation temperature thereof rises to exceed a predetermined value.
In amplifier circuits used in audio apparatus, particularly power amplifier circuits, rise in the power source voltage for the amplifier circuits and rise in the operation temperature thereof due to heat generation of the circuit components per se possibly give rise to deterioration or destruction of the circuit components of the amplifier circuits, particularly those circuit components arranged at the output stage thereof. In this field, it is common practice to employ separate protection circuits to protect the circuit components from deterioration or destruction due to the power source voltage rise and the operation temperature rise, respectively. Such a scheme, however, needs larger number of circuit components for the protection circuit construction, thus resulting in expensive protection circuits.